Description:
https://gateway.envoyproxy.io/latest/contributions/contributing/#fixing-dco

In this contributing page, the squash link: https://gitready.com/advanced/2009/02/10/squashing-commits-with-rebase.html broken:

Seems the site is down or domain problem.

Shell we replace this link to another one? like: https://www.git-tower.com/learn/git/faq/git-squash

Please provide some suggestions, I can fix it.